The present inventions relates to an array antenna receiving apparatus for removing interference by controlling directivity of an antenna, and especially, to an array antenna receiving apparatus for conducting calibration of a plurality of radio receiving sections.
In a cellar mobile communication system and so forth, in order to aim at high speed and high quality of a signal, and increase of a capacity of members, a method of forming a reception directivity pattern has been investigated, in which, using an array antenna receiving apparatus consisting of a plurality of antenna elements, a reception gain is increased for a direction along which a desired signal comes, and a reception gain is decreased for interference from other users and interference due to a delay wave.
By the way, in the array antenna receiving apparatus, since generally an amplitude variation and a phase variation in a radio receiving section for each antenna element are individually different from each other, it is necessary to compensate those amplitude variation and phase variation in forming the reception directivity pattern. This operation called calibration.
In the array antenna receiving apparatus for conducting this kind of calibration, for example like a calibration device in an array antenna radio receiving apparatus disclosed in JP-A-46180/1999, amplitude and phase information for compensation is obtained by inputting known calibration signals to each radio receiving section and measuring an amplitude variation and a phase variation.
FIG. 6 is a block diagram showing one arrangement example of a conventional array antenna receiving apparatus for conducting calibration.
As shown in FIG. 6, this conventional example is constructed of an array antenna 601 consisting of a plurality of antenna elements 602-1 to 602-N, multiplex circuits 603-1 to 603-N for multiplying calibration signals by signals received at the antenna elements 602-1 to 602-N and outputting them, which are provided in accordance with the antenna elements 602-1 to 602-N, respectively, radio receiving sections 604-1 to 604-N for conducting reception processing of signals output from the multiplex circuits 603-1 to 603-N, which are provided in accordance with the antenna elements 602-1 to 602-N, respectively, a detection circuit 611 to which signals output from the radio receiving sections 604-1 to 604-N are input, for detecting amplitude information and phase information of the signals received at the antenna elements 602-1 to 602-N based on the input signals, user signal processing sections 605-1 to 605-M, provided by the number of users, for correcting the signals output from the radio receiving sections 604-1 to 604-N using the amplitude information and phase information detected at the detection circuit 611, and outputting them as demodulation signals for every user, a signal generator 607 for calibration, which generates calibration signals, a radio transmitting section 608 for calibration, which applies frequency conversion to the calibration signals generated at the signal generator 607 for calibration, and outputting them, and power level variable circuit 609 for outputting the calibration signals output from the radio transmitting section 608 for calibration at arbitrary power levels, and the calibration signals output from the power level variable circuit 609 are multiplied by the signals received at the antenna elements 602-1 to 602-N in the multiplex circuits 603-1 to 603-N.
In the antenna elements 602-1 to 602-N constituting the array antenna 601, restrictions are not especially imposed on directivity within a horizontal plane and a perpendicular plane for a single antenna element, and for example, omini (non-directivity) and dipole (dipole directivity) can be given. The antenna elements 602-1 to 602-N are placed so that reception signals of the respective antenna elements 602-1 to 602-N have a correlation with each other, and receive signals in which desired signals and a plurality of interference signals are multiplied.
In the multiplex circuits 603-1 to 603-N, the calibration signals output from the power level variable circuit 609 are multiplied by the signals received at the antenna elements 602-1 to 602-N in a radio band by means of code multiplexing and so forth for example, and are output to the radio receiving sections 604-1 to 604-N. In addition, a multiplexing method here is not limited to the code multiplexing. Also, the calibration signals multiplied at the multiplex circuits 603-1 to 603-N can be extracted.
The radio receiving sections 604-1 to 604-N are constructed of a low-noise amplifier, a band-limitation filter, a mixer, a local dial device, an AGC (Auto Gain Controller), a quadrature detector, a low band pass filter, an analog/digital converter and so forth. Here, in the radio receiving section 604-N for example, a signal output from the multiplex circuit 603-N is input thereto, and amplification, frequency conversion from a radio band to a base band, quadrature detection, analog/digital conversion and so forth of the input signal are conducted, and the signal is output to the user signal processing sections 605-1 to 605-M and the detection circuit 611. Generally, to make power levels of output signals constant independent of power levels of input signals for each of the radio receiving sections 604-1 to 604-N, an AGC that is a non-linear circuit is used.
In the detection circuit 611, signals output from the radio receiving sections 604-1 to 604-N are input thereto, and calibration signals are extracted from the input signals, and thereby, amplitude and phase information of the signals received at the antenna elements 602-1 to 602-N is detected. The detected amplitude and phase information is output to the signal processing sections 605-1 to 605-M. Here, the amplitude and phase information of the signals received at the antenna elements 602-1 to 602-N is detected by investigating variation quantity of amplitude and phase of the calibration signals in the radio receiving sections 604-1 to 604-N.
In the user signal processing sections 605-1 to 605-M, the signals output from the radio receiving sections 604-1 to 604-N and the amplitude and phase information detected at the detection circuit 611 are input thereto, and the signals output from the radio receiving sections 604-1 to 604-N are corrected based on the amplitude and phase information detected at the detection circuit 611, and thereby, a reception directivity pattern is formed such that, for each user, a reception gain is increased for a direction along which a user signal comes, and a reception gain is decreased for interference from other users and interference due to a delay wave, and demodulation signals received by means of the reception directivity pattern are output.
In the signal generator 607 for calibration, calibration signals are generated in a base band, and the generated calibration signals are output to the radio transmitting section 608 for calibration.
In the radio transmitting section 608 for calibration, the calibration signals in the base band, which were output from the signal generator 607 for calibration, are input thereto, and digital/analog conversion, frequency conversion from a base band to a radio band and so forth are applied to the input calibration signals, and these calibration signals are output to the power level variable circuit 609 as calibration signals having a frequency band same as the signals received at the antenna elements 602-1 to 602-N.
In the power level variable circuit 609, the calibration signals output from the radio transmitting section 608 for calibration are output to the multiplex circuits 603-1 to 603-N at arbitrary power levels.
Below, an operation of the array antenna receiving apparatus arranged as described above will be explained.
In each signal received at the antenna elements 602-1 to 602-N, a desired (user) signal component and an interference signal component, and a thermal noise are included. Further, multi-path components are included in the desired signal component and the interference signal component, respectively. Usually, those signal components come from directions different from each other.
In the array antenna receiving apparatus shown in FIG. 6, using the amplitude and phase information of each signal received at the antenna elements 602-1 to 602-N, the respective signal components which come from directions different from each other are distinguished from each other, and a reception directivity pattern is formed.
At that time, in case that an amplitude and phase of reception signals inside the radio receiving sections 604-1 to 604-N are changed by each circuit included in the radio receiving sections 604-1 to 604-N, information different from the amplitude and phase information of each signal received at the original antenna elements 602-1 to 602-N is provided to the user signal processing sections 605-1 to 605-M, and it becomes impossible to exactly distinguish the signal components from each other, and to form a reception directivity pattern.
Accordingly, the calibration signals having a frequency band same as the signals received at the antenna elements 602-1 to 602-N are multiplied by the reception signals, and in the detection circuit 611, the calibration signals are extracted from the signals output from the radio receiving sections 604-1 to 604-N, and amplitude and phase information of the reception signals is detected based on a variation of the amplitude and phase of those calibration signals, and thereby, correction is applied to the amplitude and phase information of the reception signals input to the user signal processing sections 605-1 to 605-M.
Also, in non-linear controllers (especially in AGCs) included in the radio receiving sections 604-1 to 604-N, since manners of a variation of the amplitude and phase of the reception signals are different from each other dependent on power levels of the reception signals, the calibration signals of the respective outputs from the radio receiving sections 604-1 to 604-N are extracted while power levels of the calibration signals are changed by means of the power level variable circuit 609, amplitude and phase information of the reception signals is detected based on a variation of the amplitude and phase of those calibration signals, and thereby, correction quantity to be applied to the amplitude and phase information of the reception signals input to the user signal processing sections 605-1 to 605-M is determined for every power level of each calibration signal.
In the array antenna receiving apparatus having such calibration means, even though the amplitude and phase of the reception signals are changed inside the radio receiving sections 604-1 to 604-N when the array antenna receiving apparatus works, the amplitude and phase information of the reception signals input to the user signal processing sections 605-1 to 605-M can be corrected. Also, when the apparatus does not work, calibration can be conducted with high accuracy in accordance with the power levels of the reception signals.
In this manner, in this conventional example, by using the amplitude and phase information of each signal received at the antenna elements 602-1 to 602-N, it is possible to exactly distinguish the signal components from each other, which come from directions different from each other, and to form a reception directivity pattern.
Generally, in the array antenna receiving apparatus having the plurality of antenna elements, when it works, the power levels of the reception signals are changed in time for each antenna element.
Here, in the above-mentioned conventional array antenna receiving apparatus, since an amplification rate is automatically controlled in the AGC within the radio receiving sections so that a sum of the power levels of the reception signals and the power levels of the calibration signals becomes constant, in case that the power levels of the reception signals are changed, even though the calibration signals having constant power levels are input to the radio receiving sections, the power levels of the calibration signals included in the signals output from the radio receiving sections become unfixed.
During calibration, the calibration signals input to the respective radio receiving sections are compared with the calibration signals included in the signals output from the respective radio receiving sections, and thereby, amplitude and phase variations of the calibration signals in the respective radio receiving sections are detected, and based on this detection result, amplitude and phase information of the signals received at the antenna elements 602-1 to 602-N is detected.
However, if, as mentioned above, the power levels of the calibration signals included in the signals output from the respective radio receiving sections become unfixed, it is not possible to exactly detect the amplitude and phase variations of the calibration signals in the respective radio receiving sections, and the calibration cannot be conducted with high accuracy.
The present invention is made to solve the above-mentioned problems.
An objective of the present invention is to provide an array antenna receiving apparatus capable of conducting calibration with high accuracy even in an operation.
In order to accomplish the above-described objective, an array antenna receiving apparatus of the present invention has an array antenna consisting of N (N is an integer more than or equal to 1) antenna elements, N radio receiving sections for conducting reception processing of signals received at the above-described antenna elements, calibration means for multiplying calibration signals by the signals received at the above-described antenna elements, extracting the above-described calibration signals from signals output from the above-described radio receiving sections, and detecting amplitude and phase information of the signals received at the above-described antenna elements based on the extracted calibration signals, and M (M is an integer more than or equal to 1) user signal processing sections for correcting the signals output from the above-described radio receiving sections based on the amplitude and phase information detected at the above-described calibration means, and outputting them as demodulation signals, and
it is characterized in that the above-described calibration means multiplies the above-described calibration signals by the signals received at the above-described antenna elements at power levels determined based on power levels of the signals output from the above-described radio receiving sections.
Also, the above-described calibration means is characterized in that it has:
N multiplex circuits for multiplying calibration signals by the signals received at the above-described antenna elements;
a signal generator for calibration, which generates the above-described calibration signals;
a signal radio transmitting section for calibration, which applies frequency conversion to the calibration signals generated at the above-described signal generator for calibration and outputs the calibration signals having a frequency band same as a frequency of the signals received at the above-described antenna elements;
a signal processing section for calibration, which extracts the above-described calibration signals from the signals output from the above-described radio receiving sections, detects amplitude and phase information of the signals received at the above-described antenna elements based on the extracted calibration signals, and outputs control signals for controlling power levels of the above-described calibration signals based on power levels of the signals output from the above-described radio receiving sections; and
N power level variable circuits for outputting the calibration signals output from the above-described signal radio transmitting section for calibration at power levels based on the control signals output from the above-described signal processing section for calibration, and
the calibration signals output from the above-described power level variable circuits are multiplied by the signals received at the above-described antenna elements in the above-described multiplex circuits.
The above-described calibration means is characterized in that it has:
N multiplex circuits for multiplying calibration signals by the signals received at the above-described antenna elements;
a signal generator for calibration, which generates the above-described calibration signals;
a signal radio transmitting section for calibration, which applies frequency conversion to the calibration signals generated at the above-described signal generator for calibration and outputs the calibration signals having a frequency band same as a frequency of the signals received at the above-described antenna elements;
a signal processing section for calibration, which extracts the above-described calibration signals from the signals output from the above-described radio receiving sections, detects amplitude and phase information of the signals received at the above-described antenna elements based on the extracted calibration signals, and outputs control signals for controlling power levels of the above-described calibration signals based on power levels of the signals output from the above-described radio receiving sections;
K (K is an integer more than or equal to 1 and less than N) power level variable circuits for outputting the calibration signals output from the above-described signal radio transmitting section for calibration at power levels based on the control signals output from the above-described signal processing section for calibration; and
a selection and branch circuit for selecting the calibration signals output from the above-described power level variable circuits, and distributing and outputting them to the above-described N multiplex circuits, and
the calibration signals output from the above-described selection and branch circuits are multiplied by the signals received at the above-described antenna elements in the above-described multiplex circuits.
Also, the above-described signal processing section for calibration is characterized in that it outputs the control signals such that the power levels of the calibration signals extracted from the signals output from the above-described radio receiving sections becomes to be constant.
Also, the above-described signal processing section for calibration is characterized in that it recognizes a ratio of the signals output from the above-described radio receiving sections and the calibration signals extracted from the above-described signals using a bit error rate of the calibration signals extracted from the signals output from the above-described radio receiving sections.
Also, an array antenna receiving apparatus has an array antenna consisting of N (N is an integer more than or equal to 1) antenna elements, N radio receiving sections for conducting reception processing of signals received at the above-described antenna elements, calibration means for multiplying calibration signals by the signals received at the above-described antenna elements, extracting the above-described calibration signals from signals output from the above-described radio receiving sections, and detecting amplitude and phase information of the signals received at the above-described antenna elements based on the extracted calibration signals, and M (M is an integer more than or equal to 1) user signal processing sections for correcting the signals output from the above-described radio receiving sections based on the amplitude and phase information detected at the above-described calibration means, and outputting them as demodulation signals, and
it is characterized in that the above-described calibration means multiplies the above-described calibration signals by the signals received at the above-described antenna elements at power levels determined based on power levels of the signals received at the above-described antenna elements.
Also, the above-described calibration means is characterized in that it has:
N multiplex circuits for multiplying calibration signals by the signals received at the above-described antenna elements;
a signal generator for calibration, which generates the above-described calibration signals;
a signal radio transmitting section for calibration, which applies frequency conversion to the calibration signals generated at the above-described signal generator for calibration and outputs the calibration signals having a frequency band same as a frequency of the signals received at the above-described antenna elements;
a signal processing section for calibration, which extracts the above-described calibration signals from the signals output from the above-described radio receiving sections, detects amplitude and phase information of the signals received at the above-described antenna elements based on the extracted calibration signals, and outputs control signals for controlling power levels of the above-described calibration signals based on power levels of the signals received at the above-described antenna elements; and
N power level variable circuits for outputting the calibration signals output from the above-described signal radio transmitting section for calibration at power levels based on the control signals output from the above-described signal processing section for calibration, and
the calibration signals output from the above-described power level variable circuits are multiplied by the signals received at the above-described antenna elements in the above-described multiplex circuits.
Also, the above-described calibration means is characterized in that it has:
N multiplex circuits for multiplying calibration signals by the signals received at the above-described antenna elements;
a signal generator for calibration, which generates the above-described calibration signals;
a signal radio transmitting section for calibration, which applies frequency conversion to the calibration signals generated at the above-described signal generator for calibration and outputs the calibration signals having a frequency band same as a frequency of the signals received at the above-described antenna elements;
a signal processing section for calibration, which extracts the above-described calibration signals from the signals output from the above-described radio receiving sections, detects amplitude and phase information of the signals received at the above-described antenna elements based on the extracted calibration signals, and outputs control signals for controlling power levels of the above-described calibration signals based on power levels of the signals received at the above-described antenna elements;
K (K is an integer more than or equal to 1 and less than N) power level variable circuits for outputting the calibration signals output from the above-described signal radio transmitting section for calibration at power levels based on the control signals output from the above-described signal processing section for calibration; and
a selection and branch circuit for selecting the calibration signals output from the above-described power level variable circuits, and distributing and outputting them to the above-described N multiplex circuits, and
the calibration signals output from the above-described selection and branch circuits are multiplied by the signals received at the above-described antenna elements in the above-described multiplex circuits.
Also, the above-described signal processing section for calibration is characterized in that it outputs the control signals such that a ratio of the power levels of the signals received at the above-described antenna elements and the power levels of the calibration signals output from the above-described power level variable circuits becomes to be constant.
Also, an array antenna receiving apparatus has an array antenna consisting of N (N is an integer more than or equal to 1) antenna elements, N radio receiving sections for conducting reception processing of signals received at the above-described antenna elements, calibration means for multiplying calibration signals by the signals received at the above-described antenna elements, extracting the above-described calibration signals from signals output from the above-described radio receiving sections, and detecting amplitude and phase information of the signals received at the above-described antenna elements based on the extracted calibration signals, and M (M is an integer more than or equal to 1) user signal processing sections for correcting the signals output from the above-described radio receiving sections based on the amplitude and phase information detected at the above-described calibration means, and outputting them as demodulation signals, and
it is characterized in that the above-described calibration means has:
N multiplex circuits for multiplying calibration signals by the signals received at the above-described antenna elements;
a signal generator for calibration, which generates the above-described calibration signals;
a signal radio transmitting section for calibration, which applies frequency conversion to the calibration signals generated at the above-described signal generator for calibration and outputs the calibration signals having a frequency band same as a frequency of the signals received at the above-described antenna elements;
a signal processing section for calibration, which extracts the above-described calibration signals from the signals output from the above-described radio receiving sections, detects amplitude and phase information of the signals received at the above-described antenna elements based on the extracted calibration signals, and outputs control signals for controlling power levels of the above-described calibration signals based on power levels of the signals output from the above-described multiplex circuits; and
N power level variable circuits for outputting-the calibration signals output from the above-described signal radio transmitting section for calibration at power levels based on the control signals output from the above-described signal processing section for calibration, and the calibration signals output from the above-described power level variable circuits are multiplied by the signals received at the above-described antenna elements in the above-described multiplex circuits.
Also, an array antenna receiving apparatus has an array antenna consisting of N (N is an integer more than or equal to 1) antenna elements, N radio receiving sections for conducting reception processing of signals received at the above-described antenna elements, calibration means for multiplying calibration signals by the signals received at the above-described antenna elements, extracting the above-described calibration signals from signals output from the above-described radio receiving sections, and detecting amplitude and phase information of the signals received at the above-described antenna elements based on the extracted calibration signals, and M (M is an integer more than or equal to 1) user signal processing sections for correcting the signals output from the above-described radio receiving sections based on the amplitude and phase information detected at the above-described calibration means, and outputting them as demodulation signals, and
it is characterized in that the above-described calibration means has:
N multiplex circuits for multiplying calibration signals by the signals received at the above-described antenna elements;
a signal generator for calibration, which generates the above-described calibration signals;
a signal radio transmitting section for calibration, which applies frequency conversion to the calibration signals generated at the above-described signal generator for calibration and outputs the calibration signals having a frequency band same as a frequency of the signals received at the above-described antenna elements;
a signal processing section for calibration, which extracts the above-described calibration signals from the signals output from the above-described radio receiving sections, detects amplitude and phase information of the signals received at the above-described antenna elements based on the extracted calibration signals, and outputs control signals for controlling power levels of the above-described calibration signals based on power levels of the signals output from the above-described multiplex circuits;
K (K is an integer more than or equal to 1 and less than N) power level variable circuits for outputting the calibration signals output from the above-described signal radio transmitting section for calibration at power levels based on the control signals output from the above-described signal processing section for calibration; and
a selection and branch circuit for selecting the calibration signals output from the above-described power level variable circuits, and distributing and outputting them to the above-described N multiplex circuits, and
the calibration signals output from the above-described selection and branch circuits are multiplied by the signals received at the above-described antenna elements in the above-described multiplex circuits.
Also, the above-described signal processing section for calibration is characterized in that it outputs the control signals such that a ratio of the power levels of the signals output from the above-described multiplex circuits and the power levels of the calibration signals output from the above-described power level variable circuits becomes to be constant.
Also, the array antenna receiving apparatus is characterized in that
the above-described radio receiving section comprises automatic gain controlling means for keeping power levels of output signals constant independent of power levels of input signals, and
the above-described signal processing section for calibration recognizes the power levels of the signals output from the above-described multiplex circuits based on gain information in the above-described automatic gain controlling means.
In the present invention arranged as described above, since the calibration signals to be multiplied by the signals received at the antenna elements are multiplied by the signals received at the antenna elements at the power levels such that the power levels of the calibration signals extracted from the signals output from the radio receiving section become constant, even in case that the power levels of the signals received at the antenna elements change in time, and in the radio receiving sections, output thereof are automatically controlled so that a sum of the power levels of the signals received at the antenna elements and the power levels of the calibration signals become constant, the power levels of the calibration signals extracted at the calibration means do not become unfixed, and thereby, in the calibration means, the amplitude and phase variations of the calibration signals in the radio receiving section are exactly detected, and in association therewith, the amplitude and phase information of the signals received at the antenna elements is exactly detected. Thereby, calibration is conducted with high accuracy even in an operation.